1. Field of the Invention
The present invention relates to micro switches, and more particularly to thermally induced pressure operated optical switches employed in display devices, projectors or like apparatuses.
2. Prior Art
Micro-Electro-Mechanical Systems, or MEMS, is a rapidly growing technology for the fabrication of miniaturized electronic devices. MEMS employs processes similar to those used in the integrated circuit industry. MEMS technology provides a way to integrate mechanical, fluidic, optical, and electronic functionality in micro-devices, which range in size from 0.1 microns to one millimeter. MEMS devices have two important advantages over conventional counterparts: first, like integrated circuits, they can be fabricated in large numbers, so that the cost of production can be reduced substantially; second, they can be directly incorporated into integrated circuits, so that far more complicated systems can be made than with other technologies.
In certain kinds of MEMS devices, fluid can be moved through the MEMS device by the growing and collapsing of vapor bubbles. A vapor bubble is formed in each of cavities by an imbedded resistive heater. The cavity is connected to a nozzle on one side and a diffuser on the other, so that the cavity preferentially biases flow of the fluid from the nozzle to the diffuser. In practice, a bubble is periodically nucleated in the chamber, and the bubble pushes fluid from the chamber. Subsequently, the bubble collapses and pulls fluid back into the chamber. Both the expansion and the collapse are supposed to result in a net flow of the fluid from the nozzle to the diffuser.
Taiwan Pat. No. 503,332, issued on Sep. 21, 2002, discloses a reflection type optical switch employing a thermal bubble ink-jet printing apparatus and working fluid. The optical switch is represented in FIG. 7 hereof with the reference numeral 2. A detailed explanation of the configuration of the optical switch 2 is provided hereinbelow.
The optical switch 2 includes a transparent polygonal cylinder 21, a plurality of coupling glasses 23, working fluid 25, and pushing devices 27. The polygonal cylinder 21 has a plurality of side surfaces 212. The coupling glasses 23 are located adjacent to the side surfaces 212 respectively, to form a plurality of slits 232 between the coupling glasses 23 and the side surfaces 212. The working fluid 25 is contained in the slits 232. The working fluid 25 has a reflective index the same as that of the polygonal cylinder 21 and the coupling glasses 23.
The pushing devices 27 are thermal bubble ink-jet printing apparatuses, and each of them includes an imbedded heater (not labeled). When the heater is turned on, a vapor bubble 271 is created in the corresponding slit 232. By continuing to heat the vapor bubble 271, it expands to push the working fluid 25 out of the slit 232. When the heater is turned off, the temperature of the vapor bubble 271 decreases. The vapor bubble 271 collapses, and the working fluid 25 is pulled back into the slit 232 again.
In operation, an optical beam is directed into the transparent polygonal cylinder 21. When the optical beam transmits to a side surface 212 where the working fluid 25 has been push out from the corresponding slit 232, the optical beam is totally reflected. When the optical beam transmits to a side surface 212 where the working fluid 25 is contained in the corresponding slit 232, the optical beam totally passes through. The optical switch is used in optical fibers, to dynamically reconfigure the interconnection of optical beam paths. This is done by thermally controlling the presence or absence of working liquid in a slit at which a plurality of coupling glasses is located. Alternatively, the slit may be located where other kinds of optical waveguide segments intersect.
However, the above-described optical switch is generally limited in application, and does not manipulate light for viewing by humans.